In a wireless multiple access communication system, the wireless traffic channel resource, e.g., bandwidth and time interval, is shared by all the wireless terminals, i.e., mobile units, in a particular cell. Efficient allocation of this traffic channel resource is very important, as it directly impacts the utilization of the traffic channel resource and the quality of service perceived by individual wireless terminal users. One such wireless communications system is the Orthogonal Frequency Division Multiplexing (OFDM) based Spread Spectrum Multiple Access system.
In a traditional wireless system, the traffic channel resource is managed by use of rate allocation. In particular, a dedicated control channel is typically established between a base station and a particular wireless terminal. The base station then allocates to the wireless terminal a traffic channel having a prescribed transmission rate through control message exchange on the dedicated control channel. Once the transmission rate allocation is completed, the wireless terminal may use the allocated traffic channel for an indefinite duration. When the traffic requirement changes, the base station and the wireless terminal change the transmission rate of the traffic channel again through control message exchange. A problem with this control message based transmission rate allocation arrangement is that in general the control message exchange can take quite a significant amount of time to complete and, consequently, the traffic channel resource allocation process may be quite inefficient. Specifically, assume that control message exchange takes time T to be completed. Suppose that a traffic channel has already been assigned to a wireless terminal. Further assume that there is some idle interval during which the assigned wireless terminal has no traffic to be transmitted. Then, it is impossible to allow another wireless terminal to utilize the traffic channel resource in the idle interval that is less than T, thereby resulting in under utilization of the traffic channel resource. In another example, assume that “low” priority traffic has been transmitted for one wireless terminal, then when “high” priority traffic arrives for another wireless terminal, the base station has to change the traffic channel resource allocation from the wireless terminal having the low priority traffic to the wireless terminal having the arriving high priority traffic. Exchanging control messages to realize the required traffic channel allocation change introduces latency in transmission and/or reception of the high priority traffic, which is extremely undesirable.